Oxalate production at different initial Pb²+ concentrations and the influence of oxalate during solid-state fermentation of straw with Phanerochaete chrysosporium

The production of oxalate at different initial Pb²⁺ concentrations during solid-state fermentation of straw with Phanerochaete chrysosporium was investigated. It was found that the maximal peak value of oxalate concentration (22.84 mM) was detected at the initial Pb²⁺ concentration of 200 mg kg⁻¹ dry straw, while the minimum (15.89 mM) at the concentration of 600 mg Pb²⁺ kg⁻¹ dry straw, and at moderate concentration of Pb²⁺ the capability of oxalic acid secretion was enhanced. In addition, it was also found that more oxalic acid accumulation went together with better Pb²⁺ passivation effect and higher manganese peroxidase (MnP) activity. The present findings will improve the understandings of the interactions of heavy metals with white-rot fungi and the role of oxalate in lignin degradation system, which could provide useful references for more efficient treatment of Pb-contaminated lignocellulosic waste.     

Two Rubisco activase isoforms may play different roles in photosynthetic heat acclimation in the rice plant

Studies on some plant species have shown that increasing the growth temperature gradually or pretreating with high temperature can lead to obvious photosynthetic acclimation to high temperature. To test whether this acclimation arises from heat adaptation of ribulose 1,5‐bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) activation mediated by Rubisco activase (RCA), gene expression of RCA large isoform (RCA_L) and RCA small isoform (RCA_S) in rice was determined using a 4‐day heat stress treatment [40/30°C (day/night)] followed by a 3‐day recovery under control conditions [30/22°C (day/night)]. The heat stress significantly induced the expression of RCA_L as determined by both mRNA and protein levels. Correlative analysis indicated that RCA_S protein content was extremely significantly related to Rubisco initial activity and net photosynthetic rate (Pn) under both heat stress and normal conditions. Immunoblot analysis of the Rubisco–RCA complex revealed that the ratio of RCA_L to Rubisco increased markedly in heat‐acclimated rice leaves. Furthermore, transgenic rice plants expressing enhanced amounts of RCA_L exhibited higher thermotolerance in Pn and Rubisco initial activity and grew better at high temperature than wild‐type (WT) plants and transgenic rice plants expressing enhanced amounts of RCA_S. Under normal conditions, the transgenic rice plants expressing enhanced amounts of RCA_S showed higher Pn and produced more biomass than transgenic rice plants expressing enhanced amounts of RCA_L and wild‐type plants. Together, these suggest that the heat‐induced RCA_L may play an important role in photosynthetic acclimation to moderate heat stress in vivo, while RCA_S plays a major role in maintaining Rubisco initial activity under normal conditions.     

Identification of a D-amino acid decapeptide HIV-1 entry inhibitor

Entry of human immunodeficiency virus type 1 (HIV-1) virion into host cells involves three major steps, each being a potential target for the development of entry inhibitors: gp120 binding to CD4, gp120-CD4 complex interacting with a coreceptor, and gp41 refolding to form a six-helix bundle. Using a D-amino acid decapeptide combinatorial library, we identified peptide dC13 as having potent HIV-1 fusion inhibitory activity, and effectively inhibiting infection by several laboratory-adapted and primary HIV-1 strains. While dC13 did not block binding of gp120 to CD4, nor disrupt the gp41 six-helix bundle formation, it effectively blocked the binding of an anti-CXCR4 monoclonal antibody and chemokine SDF-1alpha to CXCR4-expressing cells. However, because R5-using primary viruses were also neutralized, the antiviral activity of dC13 implies additional mode(s) of action. These results suggest that dC13 is a useful HIV-1 coreceptor antagonist for CXCR4 and, due to its biostability and simplicity, may be of value for developing a new class of HIV-1 entry inhibitors.     

Paradoxical effects of a stress signal on pro- and anti-apoptotic machinery in HTLV-1 tax expressing cells

Adult T-cell leukemia (ATL) and HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) are associated with Human T-cell lymphotropic virus type 1 (HTLV-1) infection. The viral transactivator, Tax is able to mediate the cell cycle progression by targeting key regulators of the cell cycle such as p21/waf1, p16/ink4a, p53, cyclins D1-3/cdk complexes, and the mitotic spindle checkpoint MAD apparatus, thereby deregulating cellular DNA damage and checkpoint control. Genome expression profiling of infected cells exemplified by the development of DNA microarrays represents a major advance in genome-wide functional analysis. Utilizing cDNA microarray analysis, we have observed an apparent opposing and paradoxical regulatory network of host cell gene expression upon the introduction of DNA damage stress signal. We find the apparent induction of cell cycle inhibitors, and pro- as well as anti-apoptotic gene expression is directly linked to whether cells are at either G1, S, or G2/M phases of the cell cycle. Specifically, a G1/S block is induced by p21/waf1 and p16/ink4a, while pro-apoptotic expression at S, and G2/M is associated with caspase activation, and anti-apoptotic gene expression is associated with up regulation of Bcl-2 family member, namely bfl-1 gene. Therefore, the microarray results indicating expression of both pro- and anti-apoptotic genes could easily be explained by the particular stage of the cell cycle. Mechanism and the functional outcome of induction for both pathways are discussed.     

Structures of Streptococcus pneumoniae PiaA and Its Complex with Ferrichrome Reveal Insights into the Substrate Binding and Release of High Affinity Iron Transporters

Iron scarcity is one of the nutrition limitations that the Gram-positive infectious pathogens Streptococcus pneumoniae encounter in the human host. To guarantee sufficient iron supply, the ATP binding cassette (ABC) transporter Pia is employed to uptake iron chelated by hydroxamate siderophore, via the membrane-anchored substrate-binding protein PiaA. The high affinity towards ferrichrome enables PiaA to capture iron at a very low concentration in the host. We presented here the crystal structures of PiaA in both apo and ferrichrome-complexed forms at 2.7 and 2.1 Å resolution, respectively. Similar to other class III substrate binding proteins, PiaA is composed of an N-terminal and a C-terminal domain bridged by an α-helix. At the inter-domain cleft, a molecule of ferrichrome is stabilized by a number of highly conserved residues. Upon ferrichrome binding, two highly flexible segments at the entrance of the cleft undergo significant conformational changes, indicating their contribution to the binding and/or release of ferrichrome. Superposition to the structure of Escherichia coli ABC transporter BtuF enabled us to define two conserved residues: Glu119 and Glu262, which were proposed to form salt bridges with two arginines of the permease subunits. Further structure-based sequence alignment revealed that the ferrichrome binding pattern is highly conserved in a series of PiaA homologs encoded by both Gram-positive and negative bacteria, which were predicted to be sensitive to albomycin, a sideromycin antibiotic derived from ferrichrome.     

Vascular dysfunction in type 2 diabetic TallyHo mice: role for an increase in the contribution of PGH2/TxA2 receptor activation and cytochrome p450 products

In this study, we tested the hypothesis that spontaneously diabetic TallyHo (TH) mice, a novel polygenic model for type 2 diabetes, will exhibit endothelial dysfunction associated with an increased contribution from endothelium-derived contractile factors (EDCF). The cellular mechanisms underlying the increased contribution of EDCF were explored in 16 and 30-week-old male TH and age-matched male C57BL/6J mice (n=4-9). Blood glucose and serum lipid profiles were markedly increased in the TH mice. Superoxide generation, assessed with a lucigenin chemiluminescence assay, was markedly increased in the aortae of TH mice. Endothelium-dependent vascular relaxations and contractions to acetylcholine (ACh), but not endothelium-independent relaxations to sodium nitroprusside, were impaired and vascular contractions to phenylephrine were significantly enhanced in aortae from TH mice. Nomega-nitro-L-arginine methyl ester markedly increased the ACh-induced contractions in TH mice, whereas SQ29548, a thromboxane receptor antagonist, and cytochrome P450 (CYP) inhibitors 17-octadecynoic acid and sulfaphenazole, the latter being specific for CYP2C6 and 2C9, decreased and (or) normalized the contractile response to ACh in TH mice. The present study indicates that enhanced contribution of prostaglandin H2/thromboxane A2 receptor and CYP, likely CYP2C6 and 2C9, play a critical role in the pathogenesis of increased EDCF in the aortae of type 2 diabetic TH mice.     

"观察SO2对植物的影响"实验的改进

介绍了对人民教育出版社的高中生物学必修教材第2册103页,实验12“观察二氧化硫对植物的影响”的部分改进。利用洗净的金龙鱼牌5L塑料油瓶和洗净的空矿泉水瓶等废旧物资进行实验操作。材料易于寻找,成本低廉,培养了学生“变废为宝”的节约思想;用NaOH溶液吸收装置内的SO2,避免了环境污染,培养了学生的环保意识。     

Apigenin enhances the cytotoxic effects of tumor necrosis factor-related apoptosis-inducing ligand in human rheumatoid arthritis fibroblast-like synoviocytes

Activated rheumatoid arthritis (RA) fibroblast-like synoviocytes (RAFLSs) play a central role in both initiating and driving RA. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been documented to induce apoptosis only in a small proportion of RAFLSs, which is followed by an induction of proliferation in surviving cells. Apigenin, a chemopreventive bioflavonoid, exhibits proapoptotic activity in many types of cells. In the present study, we sought to determine whether apigenin could enhance the cytotoxic effect of TRAIL on activated RAFLSs. Human RAFLSs isolated from patients with RA were treated with TRAIL (1 nM), apigenin (20 μM), or their combination, and subjected to apoptosis analysis after a 24-h incubation and proliferation analysis after a 72-h incubation. Apoptosis assay revealed that TRAIL or apigenin alone induced a marked apoptosis in RAFLS and their combination yielded a synergistic increase in RAFLS apoptosis. Immunoblotting analysis of apoptosis regulators demonstrated that combined treatment with apigenin increased caspase-3 expression and activity and decreased the Bcl-2/Bax ratio relative to treatment with TRAIL alone. The presence of apigenin significantly restrained TRAIL-induced RAFLS proliferation, coupled with restoration of the expression of two cell-cycle inhibitors p21 and p27. Moreover, the combination with apigenin blunted TRAIL-induced activation of the phosphatidylinositol 3-kinase (PI3-K)/Akt pathway. Our data collectively demonstrate that apigenin sensitizes RAFLS to TRAIL-induced apoptosis and counteracts TRAIL-dependent RAFLS proliferation, which is likely mediated through inactivation of PI3-K/Akt signaling pathway.     

MicroRNA 155 Control of p53 Activity Is Context Dependent and Mediated by Aicda and Socs1

In biological processes, the balance between positive and negative inputs is critical for an effective physiological response and to prevent disease. A case in point is the germinal center (GC) reaction, wherein high mutational and proliferation rates are accompanied by an obligatory suppression of the DNA repair machinery. Understandably, when the GC reaction goes awry, loss of immune cells or lymphoid cancer ensues. Here, we detail the functional interactions that make microRNA 155 (miR-155) a key part of this process. Upon antigen exposure, miR-155^−/− mature B cells displayed significantly higher double-strand DNA break (DSB) accumulation and p53 activation than their miR-155^+/+ counterparts. Using B cell-specific knockdown strategies, we confirmed the role of the miR-155 target Aicda (activation-induced cytidine deaminase) in this process and, in combination with a gain-of-function model, unveiled a previously unappreciated role for Socs1 in directly modulating p53 activity and the DNA damage response in B lymphocytes. Thus, miR-155 controls the outcome of the GC reaction by modulating its initiation (Aicda) and termination (Socs1/p53 response), suggesting a mechanism to explain the quantitative defect in germinal center B cells found in mice lacking or overexpressing this miRNA.